Series-multiple control.



E. F.W.IALEXANDERSON.

SERIES MULTIPLE CONTROL.

APPLICATION FILED JAN.29.19I4.

1,300,542. Patented Apr. 15, 1919.

4 SHEETSSHEET I.

WZTNESSES IAZYEAZTUR.

W Enzvsr'fi' M: A" .EXIND'EHSUAZ} E. F. W. ALEXANDERSON.

SERIES MULTIPLE CONTROL.

APPLICATION FILED JAN. 29. mm.

1,300,542. Patented Apr. 15,1919.

4 S EE SSHEET 2.

v lnVenLor: Vy itnessesz Ernst FiWAIexanderson,

His Attorneg E. F. W. ALEXANDERSON.

SERIES MULTIPLE CONTROL.

APPLICATION FILED JAN.29. 1914.

1,300,542. Patented Apr. 15,1919.

4 SHEETSSHEET 3.

F 5 y F g.4.

:2. W X 28 [S2 I; Sf? M Witnesses: I inventor:

' w Ernst F. WA iexanderson,

His Attorneg E. F. w. ALEXANDERSON.

SERIES MULTIPLE CONTROL.

APPLICATION FILED JAN.29| 1914.

1,300,542, Patented Apr. 15, 1919.

4 SHEETS-SHEET 4.

u/ /.{J\ 3 4 41c j L/KQ l m Witnesses: m InVenLorw W ErnstFWAlexandeTson.

f {Ki/p b 5 His Attorneg ERNST F. W. ALEXANDERSON, OF SGHENECTADY, NEW

ELECTRIC COMPANY, A CORPORATION YORK, ASSIGNOR TO GENERAL OF NEW YORK.

SERIES-MULTIPLE CONTROL.

Specification of Letters Patent.

Patented Apr. 15, 1919.

Application filed January '29, 1914. Serial No. 815,280.

To all whom it may concern:

Be it known that I, ERNST F. W. ALEX- ANDERSON, a citizen of the UnitedStates, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful Improvements in Series-Multiple Controls, of which the following is a specification.

My invention relates to the operation of polyphase motors from a singlephase source of supply by the use of a phase converter, and moreespecially to a method of control whereby an advantageous operation ofsuch an arrangement is secured.

The operation of polyphase motors from a single phase sourceof supply inconjuncrangement which is characterized by the tion with a phaseconverter is well known and various schemes of connecting these elements have been proposed in order to attain particular advantages. It iswell known that an ordinary induction motor having a squirrel cage orphase woundrotor may be employed as the phase converter in such asystem. Two systems of connection for the converter are illustrated inmy prevlous Patents, #901,513 and #1,150,652 respectively.

In the former is illustrated a parallel arfact that one phase of theconverter and one phase of the motor are each connected directly to thesingle phase source and in the latter is illustrated a seriesarrangement which is characterized by the fact that one I of the motor.

converter phase is serially connected between the single phase sourceand one motor phase while in. both arrangements the other converterphase or phases are connected inseries with the other phase or phasesrespectively In the parallel arrangement in order to maintain asubstantial balance between the polyphase motor currents at thedifferent loads it is necessary to alter the internal connections of theconverter phases or the voltages impressed thereon; hand the seriesarrangement has'an inherent tendency to maintain a balance-between thepolyphase currents with varying loads and by interpolating a voltage ofthe proper value in the circuit or circuits in' which the last namedconverter phase or phases aind motor phase or phases are seriallyconnected,

the value relation between the polyphase. currents and the phaserelation therebetween' approach more nearly tothat desired.

the other,

In the systems described the magnetization of the converter is effectedby means of the stator windings but I have discovered that if the rotorof the converter be provided with .a suitable winding which is excitedfrom a direct current source, it becomes possible to-wholly eliminatethe magnetizing current in the stator windings by a proper adjustment ofthe direct current excitation. This synchronous excitation by means of.the direct current winding is attended by very desirable, thoughsomewhat different, re sults in the parallel and series arrangements ofconnections. In the parallel arrangement the main advantage is that byincreasing the excitation the verter may be increased to any desired degree. In the series arrangement by the adjustment of the excitation to acertain value the desired balance of polyphase currents and thetheoretically correct phase relation of polyphase currents areautomatically and accurately maintained with varying loads,

and furthermore the power factor of the .method of control thereforwhereby a series arrangement or parallel arrangement of connections maybe effected at will according to operating conditions and also wherebythe advantages attendant upon the employment of synchronous excitation,which is independent of the stator windings of the converter, may besecured in the fullest measure.

My-invention has for another object the method of operating a combinedsystem of the kind indicated whereby the series arrangement ofconnections is effected when the motor load is variable so that balancedpolyphase currents and the theoretically correct phase relation ofpolyphase currents are automatically maintained for all motor loads andthe parallel arrangement of connections is effected when the motor load.has an approximately constant and predetermined value, and whereby withthe paral lel arrangement of connections the power factor of theconverter is varied to the desired extent. A further object of myinica-lly connected to the rotor of the phase converter. Between thesingle phase source of supply and my system, I interpose a transformerwith a divided secondary conveniently provided with taps. For making thenecessary-,connections and changes' li use a master controller of thedrum type arranged to energize contactors which close and open thecircuits. Any form of polyphase m0- tors may be used, but preferablythey will be of the induction type.

My invention will be more readily understood from the followingdescription when taken in connection] with the accompanying drawings, inwhich Figure l is a diagram ShOWing the controller connections forobtaining the desired operation. Fig. 2 is a similar diagram wherein theoperation is slightly different. Figs, 3 to 8, inclusive, are vectordiagrams showing the phase relations of the various voltages, and at thesame time showing diagrammatically the connections between the variouswindings at various steps of the method of operation shown in Fig. 1.Figs. 9 to 14;, inclusive, are similar diagrams showing 'the voltagerelations and actual connections obtained at various steps of theoperation of the artwo-phase motors, and have designated their windingsas M and M,,. For changing the single phase current obtained from thesupply to two-phase current, I have indicated diagrammatically a phaseconverter having two windings in quadrature, which I will designate as Cand C This converter will ordinarily be of the induction motor type,

and have, therefore, shown it as provided with a squirrel cage armature.Arranged upon the rotor with the squirrel cage winding, is afieldwinding F connected between slip rings. A single phase alternatingcurrent commutator machine E is mechanically 'chine E.

ably connected to the main switch lever and provided with any desiredinterlocking switches. A solenoid surrounds the movable core and, whenenergized, causes the closing of the main switch. By means of theinterlocking switches, it is possible to lock or prevent the operationof another switch prior to the opening or closing of some specifiedswitch,

To. suitably-control the energization and operation of theseelectromagneticswitches, I have provided a master controller X which maybe of' any desired type. The incoming circuits are connected to fixedcontact points 1 to 14. Cooperating with these fixed points is a.movable element, shown in development, which carries contact segmentsindicated by solid line rectangles. These segments are suitableinterconnected to effect the desired connection'between the contactpoints, and the relative positions of points and segments at the varioussteps are indicated by the dot-and-dash lines a to 70 inclusive.

The secondary S, is provided with inter mediate terminals or taps 51 and52 and the usual end terminals 50 and 53. Leading from the stud 1 of themaster controller is a connection to tap 52 of the secondary, while tap51" is connected to ground, thereby I providing a low'voltage A. C.supply for operating certain switches. As will be self-evident, allthose points which I have shown on the diagram as connected to groundmight as well be connected to a common metallic conductor if such anarrangement is found desirable, but I have used this particular mannerofillustration in order to simplify the diagram.

hen the controller is turned to position a, the switch 20 is energizedand alternating current furnished from the taps 51 and 52 of thesecondary S to the. commutator ma-' This machine E, which I shallhereinafter term'an exciter, will then operate as a series motor excitedby the field -winding F and rotate the converter, bringand short-circuitthe field winding F,. In this connection the field winding F willfurnish the necessary excitation and the circuit will include theresistances R and R By providing a short circuit around the fieldwinding F,, I make the eXciter voltage less sensitive to fluctuations incurrent, or, in other words, give the exciter the characteristics of ashunt generator. Any condition of shunting which may exist will, if theexciter is a series generator, induce pulsating currents in the exciterfield winding, and these pulsations of current will result incorresponding pulsations of voltage. ,These, in their turn, wouldincrease the original pulsation and might make the operation of thewhole apparatus unstable. Such a short circuit as I have provided will,then, prevent any appreciable pulsations of the field flux and willincrease the facility with which the phase converter will be broughtinto step after an interruption of power. At this step switches 39 and42 will also-be energized and converter phase A will be therebyconnected to the end terminals 54 and 59 of 8,. An interlock providedupon switch 42 prevents the closing of switch 40,.and the current forswitch 39 is supplied through an interlock on switch 38. By theenergization of one phase of the converter, I cause this machine to runas a single phase induction motor, at the same time driving the machineE as an exciter.

It should be noted that the exciter is not wholly dependent upon its ownresidual magnetism for building up its field, but that the inducedcurrent in the secondary circuit of the converter, which pulsates slowlywith the frequency of the slip, will assist in building up the field.After the exciter field has been thus built up, it will furnishsufficient current as a generator to the'winding F of the converter todraw the same into synchronous speed, which latter will be maintained aslong as the machines so run.

Fixed point 5 on the master controller is suitably connected to theexciter circuit so that a supply of direct current is obtained throughthe short circuit around field winding F, and the switch 24 which willenergize the remaining switches as may be desired.

()n' turning the controller to step 0, switches 21. 24. and 39 willremain closed, as, in fact. they do throughout all.of the re.- mainingsteps. Switch 38 will then be energized and through its interlock caus adroping out of switch 42. At the same time switch 40 will be closed andwhen closed will short circuit the interlock on switch 42.

Interposed in one of the circuits leading from fixed point 6 in thecontrolleris a reversing switch which may close either circuit 71 or 72.In case circuit 71 is closed, switches 44 and 45 will be energized andwill lock 43 and 46. In case circuit 72 be closed,

,on the secondary S through the resistance R, to the permanentconnection between m0- tor phase A and converter phase B. The subsequentclosing of switch 34 short circuits this resistance and at the same timelocks switch 35. It should'be here noted that the secondary S isprovided with the usual end terminals 54 and 59 and with otherintermediate terminals or taps 55, 56, 57 and 58. At this Iposition 0 ofthe controller, it will be seen t at switches 21, 38, 39, 40, 44 and 45are energized and they remain energized throughout the remaining steps.These, together with the closing of switches 31 and 34, effect theconnections illustrated dia grammatically in Fig. 3. The correspondingphasesof motor and converter are connected in series, and the voltageimpressed on motor phase A and converter phase A is equal to thatinduced in secondary S plusthat induced between taps 54 and 55 of Swhile leading from tap 56 upon S, has been closed through the resistanceR while the subsequent closing of switch 35 short circuitsthis'resistance. In this position of the controller the resultingconnections are illustrated in Fig. 4, in which it will be seen that thejoint connection of motor phase A with converter phase B has been movedfrom tap 55 on S to tap 56. The voltage impressed on phase A of motorand converter has been thereby increased, while the interpolated voltageon phase B has been substantially simultaneously decreased.

At step e switches 37 and 35 will open and switches 32 and 34 willclose. The closing of switch 32 locks switches 31 and 33 and closes thecircuit leading to 34, which in turn locks Asin the previous operation,switch 34 merely serves to short circuit the resistance 1%,,whilesw'itch 32- has moved the joint connection of M and C from the tap56 to the tap 57 of 8,. as shown in Fig. 5, thereby increasing theimpressed voltage 1 sition the resulting connections are illuswderstood, however, that motor on the phase A and decreasing theinterpolated voltage on the phase B If the controller is then moved tostep 7, switches 32 and 34 will be opened, while 36 and-35 will beclosed. The closing of switch 36 looks 37 and 33 and closes the circuitfor 35, which in turn locks 34 and short circuits the resistance R Atthis step the. connections resulting are illustrated in Fig. 6, fromwhich it will be seen that the ]0lI1t connection of M and 0,, has beenmoved to tap 58 of S with the result that the voltage impressed on phaseA has been increased, while the interpolated voltage on phase B has beenreduced to zero. An inspection of Fig. 1 will show, however, that oneterminal of M is connected to one terminal of Oh through switch 45,while the other terminal of M is connected by means of switches 44, 36and 35 to the other terminal of O thereby keeping these phases inseries. Since, however, there is no interpolated voltage the voltage ofthe two will be in phase an in quadrature to the voltage in M...

At step 9 switches 36 and 35 are opened, while 33 and 34 are closed. Theclosing of 33 loclgs 32 and 36 and energizes 34, which locks 35 andshort circuits R At this p0- trated in Fig. 7 from which it will be seenthat the joint connection of M. andC has been moved to the end terminal'59 of S Since M remains connected to tap 58 of 8,, the phase of thevoltage interpolated in phase B has been reversed from that obtained insteps a, d and 8. At the same time the impressed voltage on hase A hasbeen increased and an interpolated Voltage again inserted in phase B.

If the controller be now moved to step k, the same switches which wereclosed in step 9 will remain closed, and in addition switches 41' and 42will 'be closed. By means of switch 41 a connection is establishedbetween tap 50 on S and tap 55 on S while by means of switch 42 aconnection is estab dicated diagrammatically in Fig. 8. Since thediagram not only represents the connections, but also voltage relationsin various windings, the parallel connection-which has, been establishedbrings the voltages in phase A of motor and converter and in secondariesS and S in phase. It will be unhase .A receives a voltage equivalent tot at induced in S while converter hase A receives a voltage equivalentto t at induced in S On motor phaseB an interpolated voltage equal tothat induced between taps 58 and v59 of S 'is inserted. It will be notedthat nated the two phases of the converter as C the voltages impressedfrom the transformer windings S and 8,, upon the windings M and Ca,connected in parallel, have been so chosen that the voltages impressedon the motor phases M and M are balancedand, consequently, the currentstherein are balanced.

If the controller be now moved to step i,

switch 22 will be energized, which will short circuit resistance R inthe excitercircuit; otherwise, the connections will remain as at step b.This short-circuiting of the resistance R, will cause an increase of theexcitation impressed in field F and thereby an increase in the wattlesscurrent generated by the converter and supplied to the motor.

At this step it should be noted that the rela- 1 but will also energizeswitch 23 and thereby short circuit the resistance R,. This will cause afurther increase of the excitation of the converter and a cumulativeeffect such as that just now described.

As was described in the early part of the specification, the parallelconnection of motor and converter-is not altogtherdesirable for therunning position, however desirable it may be during acceleration. Ihave therefore, provided an additional step 70 on the controller whichrestores the connections to those established at step 5 illustrated inFig. 7, as the last step in the series connection. I find that this ismost desirable for running, since with variable loads an automaticbalance is obtained. I In Fig. 2 I have illustrated the connec 'tionsfor carrying out a slightly different operation from that described inconnection with Figs. 1 and 3 to 8, inclusive. In this case theinterpolated voltage on one phase is kept constant, while the im ressedvoltage on the other phase is varie and the connection changed fromseries to parallel in a similar manner as previously. Referring to Fig.2 it will be seen that I have designated the primary'of the transformeras P and have located thereon tap 160, from which the supply ofalternating current for operating certain of the switches is obtained.The two secondaries S and S correspond in construction to S and S andthe taps 150 to 159, inclusive, correspond to the taps 50 to 59,inclusive, in Fig. 1. I have desig- E to drive the same as a motor.

switches remain the same, as does the location of the reversing switch70. Since the movement of the controller will result in the energizationof similar switches as in Fig. 1, and the interlocks remain the same, itwill be necessary for a description of this figure 'merely to refer tothe actual connections produced, without reciting in detail themeans-f0r producing them.

l/Vhen the controller is moved a step a, alternating current is suppliedto the exciter Since the secondary S is not provided with a ground, thecurrent flows through the ground on M and thence to the tap 151 on S Atstep b one phase C of the converter will be connected across thesecondary S, to start the same as an induction motor driving the machineE as a generator.

At step c the connections indicated in Fig. 9 will result, from which itwill be seen that a voltage equal to that induced between taps 150 and151 on S is impressed on phase D of motor and converter, while on phaseC there is impressed a voltage equal to that induced in S plus thatinduced between taps 154 and 155 on S,.

At step d the only change is in moving the terminal of M to tap 156 onS, thereby increasing the impressed voltage on phase C. Here, as in allof the other steps, the

, interpolated voltage on phase D remains the same. At step 6 M is movedto tap 157 on S,, while at step f it is moved to tap 158. At step 9, thelast of the series connection, M is movedto tap 159 on S,, wherebythetotal voltage of the transformer secondary is impressed on phase C.

The next step it changes to the parallel connection in a similar manneras in the previous arrangement, and the voltage impressed on M is equalto that induced in S while that impressed on C is equal to that-inducedin S.

At steps 2" and 7" the excitation of the converter field F is increasedby short-circuiting the resistances R, and R while step k theconnections are changed-back to those illustrated in Fig. 13, inorder toobtain a su itable; running condition.

It should be noted that in all thevector diagrams shown in Figs. 3 to14. in"lusi ve, the lengths of vectors represent the relative values ofthe voltages on the various wmdthe converter phases.

ings, while their angular relations represent the phase relat1ons ofthese voltages. At the same time, these diagrams represent the actualconnections between the various windings obtained at the several stepsin my control. Whether the particular operation used is that indicatedin Figs. 3 to 8, or in Figs. 9 to 14, it will be seen that I haveoutlined a method of control for polyphase motors energized from asingle phase source of supply with the "useQof a phase converter. By theparticular arrangement employed I am enabled to get a balanced conditionof motor voltages, as will be seen from an inspection of the Variousdiagrams, in which the motor voltages are always substantially inquadrature and of substantially equal magnitude.

Furthermore, I have shown two examples of a method of control wherebythe v advantages resulting from both series and parallel connections ofconverter and motor have been utilized to advantage. In accelerating theseries connection is first usedand the impressed voltage on phase A orphase C gradually increased in order to obtain an increase 1n torque.-At'the same time, the lnterpolated voltage is either varied accordingto the method used in Figs. 3 to 8, or is allowed to remain constant, asin'Figs. 9 to 14. Although the employment of an inter polated voltageand the variation thereof is not essential to the acceleration of them0- tor, nevertheless its use, in the modification shown in Fig. 1,enables the voltage in phase B to be adjusted simultaneously with thatin phase A and this is accomplished, with the connections correspondingto Figs. to 6 inclusive, by inserting the interpolated voltage in phaseB in opposition to that gener ated in said phase. A reduction in saidinterpolated voltage therefore results in an increase in the effectivevoltage in the phase. With the connections corresponding to Fig. 7 3 theinterpolated voltage assists the voltage generated in phase B and hencethe effective voltage in phase B is increased.

The employment of a winding, associated with the single phase source ofenergy, for the purpose of interpolating a voltage in phase B of themodification of Fig. 1 and phase D of themodification of Fig. 2 alsofacilitates the response of the conditions in the single phase mains tothe conditions in After the maximum torque of which the seriesconnection is capable has been obtained, a transfer is made to theparallel connection and the excitation of the converter then increasedin order to simultaneously increase the torque while obtaining thedesired correction of power factor in the motor. After the motor hasbeen fully accelerated, the motor and converter I conceive that variousmodifications of the particular arrangements herein outlined .mightreadily be made, and I therefore do tion motors provided with squirrelcage windings. With motors of another type it might .be found desirable.to use another sequence of operation or to omit certain steps whicha're'used in the particular system illustrated. The essentialcharacteristic of my invention is that I secure the advantages whichresult fromthe use of both the parallel and the series connection ofphase converter and polyphase load. The particular arrangement of theexciter so that the same may be used both as astarting motor and as anexciter, and the method of utilizing the same in connection with thephase converter have not been'herein claimed, because these features areclaimed in my co-pending application Serial No. 113,483, filed August 7,1916.

Although the relatively movable elements of the converter have beenreferred to in several instances as stator and rotor it is of courseunderstood that either element may constitute the stationary orrotatable element.

' Certain portions of the subject matter,

illustrated and described in this application,

February '23, 1917, and Serial No. 150,413, filed February 23, 1917. Inthe former application is described and claimeda system involving aphase converter or balancer of the induction motor type comprisingrelatively rotatable members, one of which is provided with a squirrelcage winding and means for synchronously exciting the converter and theotherof which is provided with windings connected to the load circuitand the supply circuit according to the series arrangement hereinbeforedescribed. and in the latter application is described and claimed asystem involving a phase converter or balancer of the induction motortype comprising relatively rotatable members, one of which is providedwith a squirrel cage winding and means for synchronously exciting theconverter, and the other of which is provided with windings connected tothe load circuit and the supply circuit according to the parallelarrangement of connections hereinbefore described.-

Vhat I claim as newand desire to secure by Letters Patent of the UnitedStates, is,-

1. The method of operating a system of phase conversion, in which apolyphase load circuit derives its energy from a single phase source bymeans of a phase converter, which consists in having one load phaseconnected in series with one converter phase to said source when thepolyphase load is variable and in having said load phase and saidconverter phase independently connected to said source when thepolyphase load approximates apredetermined value.

2. The method of operating a system of phase conversion, in which apolyphase load circuit derives its energy from a single phase source bymeans of a phase converter, which consists in maintaining one load'phaseconnected in circuit with one converter phase, and in having anotherload phase connected in series with another converter phase to saidsource when the polyphase load is variable and in having the secondnamed load phase and the second named converter phase independentlyconnected to said source when the polyphase-load approximates apredetermined value.

3. The method of starting a polyphase motor from a single phase sourceby means of a phase converter which consists in connecting one motorphase and one converter phase in series with each other to said singlephase source and maintaining such connection while the motor torque ischanging and then connecting said motor phase and said converter phaseindependently of each other to said single phase source.

4. The method of operating a system comprising a polyphase motor, asingle phase source of energ and a phase converter'of. the polyphasemotor type adapted t be synchronously excited independently of saidsource, which consists in maintaining one motor phase connected incircuit with one converter phase, and in having another motor phaseconnected, in series with another converter phase, to said source andmainphase independently connectedto said source and either maintainingor increasing the converter excitation, when th motor load approximatesa predetermined value.

The method of controlling a polyphase motor deriving energy from asingle phase line through a phase converter, of which one phase isconnected to one phase of the motor, and another phase is connected inseries with another phase of the motor, which consists in interpolatinginto said first-named circuit a-voltage different in value from thatphase is connected to one phase of the motor, and another phase isconnected in series with another phase of the motor, which consists ininterpolating into said first-named circuit a volt-age different invalue from that line through a phase converter, of which one phase isconnected to one phase of the motor, and another phase is connected inseries with another phase of the motor, which consists in interpolatinginto said first-mentioned phase circuit a voltage different in valuefrom that of said source, impressing a voltage derived from said sourceon said series circuit, increasing the latter voltage, substantiallysimultaneously decreasing the interpolated voltage until it becomeszero, andthen interpolating a voltage of reversed phase. 7

8. The method of controlling apolyphase motor deriving energy from asingle phase line through a phase converter, of which one phase isconnected to one phase of the motor, and another phase is connected inseries with another phase of the motor, which consists in interpolatinginto said first-menr tioned phase circuit a voltage diflerent in valuefrom that of said source, impressin a voltage derived from said sourceon sai series circuit, increasing the latter voltage, substantiallysimultaneously decreasing the interpolated voltage until it becomeszero, then interpolating a voltage of reversed phase, and thenconnecting in parallel the last mentioned phases of the motor andconverter.

9. The method of controlling a polyphase motor deriving energy from asingle phase line through a phase converter, of which one phase isconnected to one phase ofthe motor. and another phase is connected inseries with another phase of the motor, which consists in interpolatinginto said first-mentioned circuit a. voltage different in value fromthat of said source, impressing a voltage derived from said source onsaid series connected phases, and then connecting these phases inparallel to the source.

10. The method of controlling a polyphase motor deriving energy. fromasingle hase line through a phase converter, of whic one phaseisconnected to one phase of the mo: tor, and another phase is connectedin series with another phase of the motor, which consists ininterpolating in said first-mentioned circuit a voltage different invalue from that of said source, impressing a voltage derived from saidsource on said series connected phases, then connecting these phases inparallel to the source, and subsequently removing said parallelconnection and again connecting these phases in series.

11. The method of controlling apolyphase motor deriving energy from asingle phase line through a phase converter, of which one phase isconnected to one phase of the mo tor, and another phase is connected inseries with another phase of the motor, which consists in interpolatingin said first-mew tioned circuit a voltage different in value from thatof said source, impressing a voltage derived from said source on saidseries connected phases, increasing said impressed voltage, and thenconnecting these phases in parallel to the source.

12. The method of controlling a polyphase motor deriving energy from asingle phase line through a phase converter, of which one phase isconnected to one phase of the motor, and another phase is connected inseries with another phase of the motor, which consists in interpolatingin said firstmentioned circuit a voltage different in value from that ofsaid source, impressing a voltage derived from said source on sandseries connected phases, increasing said impressed voltage, thenconnecting these phases in parallel to the source, and subsequentlyremoving said parallel connection and again connecting these phases inseries.

13. The method of controlling a polyphase motor deriving energy from asingle phase transformer having an unequally divided secondary windingthrough a phase converter, of which one phase is connected in serieswith one phase of the motor, which consists in connecting equal sectionsof said secondary winding in parallel, connecting a phase of said motoracross said smaller section of secondary winding, connecting a phase ofsaid converter across the larger section of said secondary winding, andinterpolating insaid series circuit a voltage different from thatinduced in either section of said secondary. I

14. The method of controlling a polyphase motor deriving energy from asingle phase line through a phase converter having a separately excitedfield winding, where one phase of the converter is connected to onephase of the motor, and another phase is connected in series withanother phase of the motor, which consists in interpolating iii saidfirst-mentioned circuit a voltage different in value from that of saidsource, impressing a voltage derived from said source on said seriesconnected phases, then connecting these phases in parallel to thesource, and then increasing the excitation of said converter fieldwinding.

15. The method of controlling a polyphase motor deriving energy from asingle phase line through a phase converter having separately excitedfield winding, Where one phase of the converter is connected to onephase of the motor, and another phase-is connected in series withanother phase of the motor, which consists in interpolating in saidfirstmentioned circuit a voltage difl'erent in value from that of saidsource, impressing a voltage derived from said source on said seriesconnected phases, then connecting these phases in parallel tot-hesource, then increaslng the excitation, of said converter field winding,and subsequently removing said parallel connection and again connectingthese phases in series.

16. The method of controlling a polyphase motor deriving energy from-asingle phase line through'a phase converter having a separately excited.field winding, where one phase of the converter is connected to onephase of the motor, and another phase is I ent in value from that ofsaid source, im-

connected in series with another phase of the -motor, Which consists ininterpolating in said first-mentioned circuit a voltage d ffer-- ent invalue from that of said source, impressing a voltage derived from saidsource on said series connected phases, increasing said impressedvoltage, then connecting these phases in parallel to the source, andthen increasing the excitation of said converter field winding.

1-7. The method of controlling a polyphase motor deriving. energy from asingle phase line through a phase converter having a separately excitedfield winding, where one phase of the converter is connected to onephase of the motor, and another phase is connected in series withanother phase of the motor, which consists in interpolating in saidfirst-mentioned circuit a voltage (llflGlfv .ent in value from that ofsaid source, im-

pressing a voltage derivedfrom said source on said series connectedphases, increasing said impressed voltage, thenconnecting these phasesin parallel to the source, then increaslng the excitation of saidconverter pressing a voltage derived from said source on said seriesconnected phases, decreasing said interpolated voltage and substantiallysimultaneously increasing said impressed voltage, then connecting theseseries connected phases in parallel to the source, and then increasinthe excitation of said converter field winding". l

19. The method of controlling a polyphase motor deriving energy from asingle phase line through a phase converter having a said parallelconnection and again connecting these phases in series. 35

20. In combination, a single phase source of supply, a phase converter,a polyphasemotor and a controller having its contacts arranged in oneoperating position of the controller to connect one phase of the motorand one phase of the converter in parallel to the source of supply, andin another operating position to connect one phase of the motor and onephase of the converter in series to the source of supply.

21. In combination, a single phase source of energy, a phase converterof the polyphase motor type, means independent of said source forproducing synchronous excitation in said phase converter, a polyphase10o motor, and means for connecting one motor phase in circuit with oneconverter phase and for connecting another motor phase and anotherconverter phase either in series with each other to said source orindependently of each other to said source. 22. In combination, a singlephase sourc of energy, a phase converter of the polyphase motor typehaving relatively movable members, one of said members having aplurality of windings, a polyphase motor, means'adapted to connect oneof said windings in circuit with one motor phase and to connect anotherof said windings and another motor phase either in series With eachother to said source or independently of each other to said source, andmeans associated with another of said members for synchronously excitingthe converter independentlyof the single phase source.

23. In combination,'a single phase source of energy, a phase converterof the polyphase motor type having relatively movable members, one ofsaid members having a plurality of windings, a polyphase motor, meansadapted to connect one of said windings incircuit with one motor phaseand to connect another of said windings and another 'motor phase eitherin series with each other to said source or independently of each otherto said source, and means 'comone phase of the converter in parallel tothe source of supply and to connect another phase of theconverter andanother phase of the motor in circuit with one another and with aportion of the winding of said transformer so as to interpolate avoltage different invalue from that of the source, and in anotheroperating position to connect the first-nai'ned phases in series to thesource.

25. In "combination, a single phase source of supply, a synchronouslyexcited phase converter, a polyphase motor, and a controller having itscontacts arranged in one operating position of the controller to connectone phase of the converter and one phase of the motor in parallel to thesource of supply, and to connect another phase of the converter tosupply energy to another phase of the motor, and in another operatingposition to connect the first-named first-named phases in series to thesource.

26. In combination, a single phase source of supply, a phase converter,a transformer interposed between the two, a polyphase motor, and acontroller having its contacts arranged in one operating position of thecontroller to connect a phase of the converter and a phase of the motorin parallel to different points of the transformer winding so thatsubstantially balanced currents are produced in the phases of the motor,and to connect another phase of the converter to deliver energy toanother phase of the motor, and in another operating position to connectone phase of the motor and one phase of the converter in series to thesource of supply.

27. In combination, a single phase source of supply, a phase converter,a transformer interposed between the two, a polyphase m'otor, and acontroller having its contacts arranged. in one operating position ofthe controller to connect one phase of the motor and one phase of theconverter in series to the source of supply and to connect another phaseof the motor to another phase of the converter in series with' a portionof said transformer winding solas to interpolate a voltage different invalue from that of said 'source, and in another operating position tochange the connections to increase the :voltage deliveredby saidtransformer to said first-mentioned circuit.

28. In rombination, a single phase source of supply, a phase converter,a transformer interposed between the two, a polyphase motor and acontroller having its contacts arranged in one operating position of thecontroller to connect one phase of the motor and one phase of theconverter in series to the source of supply, and to connect anotherphase of the motor to another phase of the converter in series with aportion of said transformer winding, so as to interpolate a voltagedifferent in value from that of said source, and in another operatingposition to change the connections to increase the voltage delivered bysaid transformer to said first-mentioned circuit, and to substantiallysimultaneously decrease the interpolated 1 voltage.

29. In combination, a single phase source of supply, a phase converter,a transformer interposed between the two, a polyphase motor and acontroller having its contacts arranged in one operating position of thecontroller to connect one-phase of the motor and one phase of theconverter in series to the source of supply, and to connect anotherphase of the motor to another phase of the converter in series with aportion of said transformer winding so as to interpolate a voltagedifferent'in value from that of said source, and in other operatingpositions to change the connections to increase the voltvage deliveredby said transformer to said first-mentioned circuit, and tosubstantially simultaneously decrease the interpolated voltage until itbecomes zero, and then in another operating position to change theconnections to interpolate a voltage of reversed phase. 1

30. In combination, a single phase source of supply, a phase converter,a transformer interposed between the two, a polyphase motor and acontroller havinc its contacts arranged in one operating position of thecontroller to .connect one phase of the motor and (one phase of theconverter in series to the source of supply, and to connect anotherphase of the motor to another phase of the converter in series with aportion of said transformer winding so as to interpolate a voltagedifferent in value from that of said source, and in other operatingpositions to change the connections to increase the voltage delivered bysaid transformer to said first-mentioned circuit, and to substantiallysimultaneously decrease the interpolated voltage until it becomes zero,and then in another operating position to change the connections tointerpolate a voltage of reversed phase, and in still anotheroperatingposition to connect the series connected phases of the motorand converter in parallel to the .source of supply.

converter, a polyphase motor, means for connecting one phase of the saidmotor in series with one phase of said converter to a portion of one ofsaid secondary windings to interpolate a voltage in said series circuit,different from that induced in either section of said secondary Winding,means for conv of supply, a synchronouslv excited phase converter, a'polyphase motor and a controller hav1ng'1t's contacts arranged .in oneoperating position to connect one phase of [snAn] the motor and onephase of the converter in series to said source of supply and to connectanother phase of said converter to supply energy to another phase orsaid motor ERNST F. W. ALEXANDERSON. Witnesses BENJAMIN B. HULL,MARGARET E. VVooLLEY.

It, is hereby certified that in Letters Patent No. 1,300,542, grantedApril 15, 1919, upon the application of Ernst F. W. Alexanderson, ofSchenectady, New York, for an improvement in Series-Multiple Controls,errors appear in the printed, specification requiring correction asfollows: Page 2, line 96, for the Word suitable, read suitably; page 3,line 10, for the word shunting" read hunting; page 5, line 21, for thearticle a read to; page 7, line 49, claim 9, for the word into read page9, line 32, claim 25, strike out the compound Word first-named; and thatthe said Letters Patent should be read with these corrections thereinthat the same may conform to the record of the case the Patent Office.

Signed and sealed this 20th day of May, A. D., 1919.

R. F. WHITEHEAD,

Acting Commissioner of Patents

